A device for controlling the inter-vehicle distance between a subject vehicle and a preceding vehicle is known (for example, Japanese Patent Application JP2007-320458A). This device operates to capture an image ahead of the subject vehicle using a camera to detect a traffic signal and a preceding vehicle located ahead and, when the traffic signal and the preceding vehicle are detected but the traffic signal then becomes undetected, control the travel of the vehicle so as to increase the inter-vehicle distance between the subject vehicle and the preceding vehicle.
However, when the subject vehicle travels to follow the preceding vehicle in an automated or autonomous manner, if the inter-vehicle distance between the subject vehicle and the preceding vehicle is increased as in the above prior art, it will be difficult to detect the traveling trajectory of the preceding vehicle. This may be problematic.